The United States Federal Aviation Administration (FAA) recognizes a takeoff (T/O) phase of flight as a criterial phase of flight. T/O is the phase of flight in which an aircraft goes through a transition from moving along the ground (taxiing) to flight. The speed required for T/O varies with aircraft performance factors including air density (affect by airport elevation and air temperature), aircraft weight, and aircraft configuration such as the position flaps and/or slats (high-lift devices). Other factors include the length and slope of the runway. In some aircraft, a flight management computer (FMC) may be programmed to determine T/O speeds.
Aircraft may employ “V-Speeds” which include V1, VR, VLOF, and V2. At speeds less than or equal to V1, the pilot may abort the T/O should a specific situation arise calling for the T/O to be aborted; above V1, the pilot may continue the T/O and return for landing. At VR, the pilot may begin “pull back on the stick”; in response, the aircraft begins to rotate about its lateral axis, and the nose wheel lifts off the ground while the main gear remains on the surface. At VLOF, the main gear leaves the surface as the aircraft lifts off and continues its acceleration. As V2 (i.e., a T/O safety speed) is reached, the aircraft may safely climb at a minimum climb gradient.
Under a typical or routine T/O phase of flight, the aircraft is placed into a T/O configuration which includes engine thrust being set at T/O power (or T/O thrust) and a deployment or an extension of flaps and/or slats. As the aircraft continues its T/O climb, the aircraft may be placed into a “clean” configuration with the retraction of flaps and/or slats; in addition, thrust may be set to a climb thrust setting as the aircraft transitions to the climb phase of flight.
If the aircraft is configured with an autothrottle (NT) system, it may be engaged during the T/O phase of flight. The A/T system may be armed after the pilot manually sets a throttle position for T/O thrust; alternatively, upon arming the NT system, mechanical actuators may drive the throttles to the T/O thrust position to align with the selection of T/O thrust mode. Thereafter, upon completion of the T/O phase, the thrust mode selection can be transitioned to climb thrust mode and A/T system may automatically drive the throttles to a climb thrust position. Because thrust may be controlled by the A/T system during the T/O phase, the pilot may place more of his or her focus on controlling the pitch attitude of the aircraft to maintain the desired T/O climb speed until the T/O phase is completed.
From time to time, a T/O phase of flight may not be typical or routine. One such time arises when a noise abatement procedure for a runway(s) is placed into effect near a noise sensitive area(s). In Advisory Circular (AC) 91-53A published by the FAA on Jul. 22, 1993 and entitled “Noise Abatement Departure Procedures” (NADP), the FAA discusses safe thrust reduction criteria for NADPs and provides two departure profiles that may provide environmental benefits to communities surrounding airports: a close-in community NADP and a distant community NADP.